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klystrackplugin

Plays the modland Klystrack corpus: chiptunes authored in Tero Lindeman's klystrack tracker (.kt), rendered by the tracker's own software synth.

How it works

A .kt file is a klystrack song: an 8-byte cyd!song signature, a format version byte, then the pattern/instrument data for klystrack's cyd software sound engine (a virtual chip with pulse/saw/noise/triangle oscillators, a wavetable, an FM operator, filters and effects). Playback is done by the engine's own bundled player library, libksnd:

  1. canHandle() gates on the cyd!song magic so unrelated .kt files are declined (Skip, not mis-play).
  2. The song is loaded from memory (KSND_LoadSongFromMemory) into a player created with KSND_CreatePlayerUnregistered — i.e. no SDL audio thread; the host pulls audio synchronously.
  3. getSamples() calls KSND_FillBuffer, which mixes the cyd engine straight into a 44100 Hz interleaved-stereo buffer. Song length is computed from KSND_GetPlayTime, and end-of-song is signalled to the host from that duration (libksnd fills silence past the end rather than short-reading).

Vendored components / licensing

Component Source License
klystron/lib/ (libksnd wrapper) + klystron/snd/ (cyd synth core) Tero Lindeman ("kometbomb"), klystron (https://github.com/kometbomb/klystron) MIT
klystron/shim/ (SDL type/endian/audio shim) this plugin MIT (same as klystron)

klystron is MIT-licensed (the license text is in klystron/macros.h), so the plugin is MIT.

The SDL shim (why klystron/shim/)

klystron's snd/ core was written against SDL for three things: SDL's fixed-width integer typedefs, its little-endian byte-swap macros, and its mutex/audio-callback plumbing. This plugin drives libksnd manually through KSND_CreatePlayerUnregistered() / KSND_FillBuffer() and builds with NOSDL_MIXER and without USESDLMUTEXES / USESDL_RWOPS, which compiles out the audio thread, mutex and RWops paths. That leaves only the integer types and endian macros as a genuine dependency; klystron/shim/SDL.h + klystron/shim/SDL_endian.h supply those (plus inert stubs for the dead cyd_register audio-device path) so the plugin links without any real SDL dependency. The vendored snd/ and lib/ sources are otherwise unmodified.

Re-vendoring

To update klystron, re-copy src/snd/*.{c,h}, src/lib/ksnd.{c,h}, src/macros.h and src/sllhdr.h from upstream into klystron/. The shim/ directory and this plugin's CMake handle the SDL-free build; no edits to the vendored sources are required (re-check the #ifdef NOSDL_MIXER / USESDLMUTEXES / USESDL_RWOPS guards if upstream reworks its audio layer).